Electrical contacts

ABSTRACT

An electrical contact comprising a high-purity nickel alloy for use in a corrosive atmosphere as, for example, in the presence of sulphur bearing materials.

United States Patent Byrne Mar. 14, 1972 [54] ELECTRICAL CONTACTS [72] Inventor: William Ralph Byrne, 722 Harris Avenue,

Providence, R.l. 02409 [22] Filed: May 1, 1969 [21] Appl.No.: 820,849

2,812,406 11/1957 Egan ..200/166C OTHER PUBLICATIONS Product Design Catalog File, Sweet s Catalog Service, F. W, Dodge Corp., N.Y., N.Y., 1960, pgs. 6 and 7, Section 2c/Sy.

Primary Examiner-L. Dewayne Rutledge Assistant ExaminerJ. Davis Att0rneyBums, Doane, Swecker & Mathis ABSTRACT An electrical contact comprising a high-purity nickel alloy for use in a corrosive atmosphere as, for example, in the presence of sulphur bearing materials.

5 Claims, 4 Drawing Figures PATENTEDHARM I972 Q, 649,795

I NVENTOR 144 /P/9Zp// BY/PNE,

ww Mf ATTORNEYS ELECTRICAL CONTACTS other apparatus which require a stable contact resistance in a COI'I'OSiVC environment.

SUMMAR OF THE DISCLOSURE An electrical contact according to the invention is excep- In the electrical Contact industry, it is important to use tionally free from non-metallic inclusions, has a low base hardtact materials which have a Stable contact resistance 5 ness and good ductility which will permit heavy cold deforma- The reaction of the contact material with its environment tion without reannealing' can cause a reaction product on the surface of the contact. An example of the chemical composition of the alloy for use Many of these reaction products are insulators or poor conas an electrical contact according to the invention is given ductors of electricity. The formation of these high resistance below in percentages by weight:

Ni C Mn Fe Cu Cr S Si Mg Ti Co Nominal $19.98 .01 .001 .001 (.001 .001 .00l .00l .00l .00l .00l Limiting 9U. 97 02 001 005 001 001 001 001 001 (X11 O01 l Maximum except nickel, which is minimum.

or insulation materials on the surface of the electrical contact This alloy is extremely malleable by metal working material will cause a high contact resistance and if this surface echni es, i e., mechanical deformation. Softness if also an layer is especially insulating, it can even prevent the flow of important characteristic of contact materials. The softness current through the contact. characteristic is important for electrical contact purposes in As an example, if copper is used as a contact metal, sulphur that the contact mechanically deforms easily to increase the or oxygen in the atmosphere will react to form copper sulactual area of contact, thereby lessening the electrical rephide or oxide on the oxide on the surface of the copper. This sistance. layer of sulphide or oxide on th urf e o e pp will The use of an electrical contactmade wholly ofthe alloy has then either cause a high contact resistance or, if the layer is 2 e nomi al advanta es over plated or clad materials. thick enough, it can prevent the flow of current across the Sulphides, ozone, and oxygen in the atmosphere around the contacts and thus cause an open circuitcontacts are particularly damaging to electrical contacts in Attempts have been made heretofore to use commercially that they are highly reactive and form insulating films on the available alloys of nickel as contact materials, but these did contact metal. Ozone is created as a result of the arcing which not show an especially Stable Cont t resi nc normally accompanies the making and breaking of electrical l have discovered that a high purity grade of nickel alloy contacts and is continuously being created in an operation containing at least 99.9 percent of pure nickel and not more where there is a voltage across the contacts when they open or than 0.1 percent of impurities has unique properties as a conclose. tact material which make it ideally suitable for low voltage and Th hi h l e conductivity is important for contacts for low current PP The unique P p y of this alloy is use in apparatus such as computers and telephone switches or its stable contact resistance which has not been found in other i li i he the current is high and R heating nickel alloys with a lower nickel content. This alloy will mainbecomes i bl Th hi h volume d i i i as i tain a low stable Contac resis nce in the pr en f sulphu portant for television tuner contacts, because actual total rebearing materials as, for example, hydrogen sulphide, alu sistance can be adjusted or compensated for in a television minum sulphide, sulphur dioxide, or pure sulphur, which tuner circuit. would cause the formation of metal sulphides with commer- It is also possible to use the high purity nickel alloy as the cial nickel alloys. This fact makes the new contact very suitaupper fa f fl ibl Contact f l i l layers as f hie for iow Voiiage and low current Woikample, over a layer of base metal to prevent atom migration.

Examples thereof are shown in FIGS. 3 and 4. BRIEF DESCRIPTION OF DRAWINGS The strip shown in diagrammatic cross section in FIG. 3 I have illustrated an application of this invention in the acy be used as a Stationary Contact for ieievisio" tuners The companying drawings, in which: major portion of the thickness of the strip is of base metal, in-

g 1 i a top plan i f a Contact board having a mp dicated at 3, having a relatively thin layer of silver alloy coated ty ofcomacts i b dd d h i on the surface thereof, as indicated at 4. The silver alloy is Fig 2 i cross Section h h h; d used primarily because of its electrical conductivity. Only a FIGS. 3 and 4 are diagrammatic sectional views showing thin surface layer of Siivei aiioy is used because high stator commas frequency current which is used only travels on the surface. A gold alloy contact element is indicated at 5 embedded in the DETAILED DESCRIPTION OF DRAWINGS surface of the silver layer 4.

In FIG. 4, a high purity nickel alloy is used as the base metal, indicated at 6, with the gold alloy contact 7 embedded in the surface thereof.

In actual use a problem is encountered in that the silver atoms migrate across the surface of the gold alloy (by surface diffusion). These silver atoms on the surface of the gold are then chemically attacked by sulphur bearing compounds in the atmosphere and form a black silver sulphide on the surface of the gold. The silver sulphide then acts as a resistance barrier to the flow of current across the contacts, and gives nonuniform tuning of the television picture.

I have discovered that by replacing the silver alloy 4 with high purity nickel alloy will eliminate the surface diffusion In the preparation of an electrical contact embodying this invention, I use a high purity nickel alloy which has a purity of not less than 99.9 percent, and preferably 99.98 percent, of nickel. This alloy is initially formed as wire which can be drawn down to a thin strip and flattened to approximately 0.015 inch thick by 0.06l inch wide in a continuous strip. The flattened alloy wire can be fabricated or used as needed as an electrical contact.

As illustrated, for example, in FIG. 1, a contact board is indicated generally by the numeral 1. This is of any suitable or desired construction and size according to the use to be made thereof. In this embodiment, the contact board is molded of plastic and has imbedded therein a suitable number of electriproblem cal contacts in accordance with the invention, generally inl have also discovered that the strip having the fl ra. dicated Pmjecting transversely through board-"in this tion shown in FIG. 4 makes a good stator material, and it is embodiment, h Contact board is used as a P of 3 easier and less costly to manufacture. The base material for contact in a television tuner. Electrical contacts according to hi strip may b 99,5 percent i k l to 99 3 percent i k l, it the invention may als be used i mP Swilcils, rotor is important, however, that the strip be manufactured so as to switches, telephone relays, telephone connectors and in any iv d f i o ie 2. An electrical contact according to claim 1, wherein the stable alloy has a nominal purity of 99.98 percent nickel.

3. An electrical contact according to claim 1, wherein the alloy forms a solid contact body.

4. An electrical contact according to claim 1, comprising a substantially flat wire of highly pure nickel having a purity of substantially 99.98 percent.

5. An electrical contact according to claim 1, wherein the stable alloy has a nominal purity of 99.98 percent pure nickel and not to exceed 0.02 percent of impurities. 

2. An electrical contact according to claim 1, wherein the stable alloy has a nominal purity of 99.98 percent nickel.
 3. An electrical contact according to claim 1, wherein the alloy forms a solid contact body.
 4. An electrical contact according to claim 1, comprising a substantially flat wire of highly pure nickel having a purity of substantially 99.98 percent.
 5. An electrical contact according to claim 1, wherein the stable alloy has a nominal purity of 99.98 percent pure nickel and not to exceed 0.02 percent of impurities. 